Typical communication systems, employing communication standards such as GSM (Global System for Mobile Communication), GPRS (General Packet Radio Service), EDGE (Enhanced Data Rates for GSM Evolution), UMTS (Universal Mobile Telecommunication Systems), and combinations (multi-mode systems), may use transceivers for transmitting and receiving signals. A transceiver can include a high gain range transmitter to transmit signals to communication devices when using any of such communication standards.
In a non-constant envelope phase modulation scheme, a baseband signal containing a baseband phase signal and a baseband amplitude signal is modulated into a high frequency carrier signal, such as a radio frequency (RF) frequency signal or RF signal, for transmission. The baseband phase signal may phase modulate the RF frequency carrier signal producing a phase modulated RF signal. The phase modulated RF signal may further be amplitude modulated by the baseband amplitude signal in a mixer component to produce the non-constant envelope phase modulated RF signal. The amplitude modulation may be sourced from a Digital to Analog Converter (DAC) which transforms the baseband amplitude signal into an analog baseband amplitude signal. The amplitude modulation may be used for exact trajectory of the phase modulated RF signal and may require a high gain range for efficient transmission in a transmitter.
Normally, a transmitter employed in a polar modulation may require a high gain range for transmitting the non-constant envelope phase modulated RF signal. However, present-day mixers are generally not capable of handling high gain ranges. To handle high gains, the mixer may require a larger size which may lead to a distortion problem during a low gain transmission of the modulated RF signal. Furthermore, the larger mixer size produces a relatively high local oscillator (LO) leakage which includes a non-zero RF signal when the baseband amplitude signal is zero. Therefore, a conventional topology of the transmitter in a typical communication device may not meet low distortion and low LO leakage requirements.